a, Previous methods involve the reduction of preformed or in situ generated (the latter from imidazolium tetrahaloaurate salts) NHC–metal (for example, gold) complexes, or the displacement of weakly bound (for example, thioether or amine) ligands with free NHCs. So far, it has not yet been possible to install NHCs onto gold nanomaterials of arbitrary size and shape with these approaches. X, a coordinating ligand, typically a halogen such as Cl or Br; R and R2, alkyl, aryl or other substituents. b, Here, we introduce a bidentate thiolate masked NHC strategy whereby exchange of CTAB ligands on commercial CTAB@Au nanorods with a photogenerated thiolate is followed by NHC installation. Shown is the synthesis of thiolate monolayer 1-Au@Au from photodeprotection of 1-Au and its subsequent reduction to generate NHC@Au-I, which introduces a new surface-bound NHC–gold adatom complex. The resulting bidentate thiolate–NHC-stabilized gold nanorods have the same size and shape as their parent commercial nanorods and are robust towards a range of stringent conditions. R3, triazole-conjugated polyethylene glycol.

Abstract: Although N-heterocyclic carbenes (NHCs) have demonstrated outstanding potential for use as surface anchors, synthetic challenges have limited their application to either large planar substrates or very small spherical nanoparticles. The development of a strategy to graft NHCs onto non-spherical nanomaterials, such as gold nanorods, would greatly expand their utility as surface ligands. Here, we use a bidentate thiolate–NHC–gold(i) complex that is easily grafted onto commercial cetyl trimethylammonium bromide-stabilized gold nanorods through ligand exchange. On mild reduction of the resulting surface-tethered NHC–gold(i) complexes, the gold atom attached to the NHC complex is added to the surface as an adatom, thereby precluding the need for reorganization of the underlying surface lattice upon NHC binding. The resulting thiolate–NHC-stabilized gold nanorods are stable towards excess glutathione for up to six days, and under conditions with large variations in pH, high and low temperatures, high salt concentrations, or in biological media and cell culture. We also demonstrate the utility of these nanorods for in vitro photothermal therapy.